The invention herein relates to phenolic adhesives. More particularly it relates to phenolic adhesives useful as adhesives for exterior grade plywood.
As is well known, plywoods are manufactured by joining layers or plies of wood veneer or of wood veneer and a lumber core with a suitable adhesive. Exterior grade plywoods are bonded with thermosetting phenol-aldehyde ("phenolic") resins because these resins are resistant to the effects of water, even boiling water. Descriptions of typical adhesives of this type and their use as plywood adhesives will be found in U.S. Pat. No. 3,755,067 issued to A. Schnabel.
Phenolic bonded plywood offers little fire resistance, as the fire penetrates the various plies of wood and adhesive rather quickly. Conseqeuntly the use of such plywood is subject to various restrictions where there are fire code requirements. It would therefore be an advantage to have a phenolic bonded exterior grade plywood which would be capable of meeting more stringent requirements for fire resistance. Such a material not only would be able to comply with more stringent fire codes, but would also offer a greater degree of safety and protection for people in buildings where it is used in walls, floors and the like.